Motor load estimation method and readable storage medium

Abstract

The invention provides a motor load estimation method and a readable storage medium. The motor load estimation method comprises the following steps: controlling a motor to start based on a preset open-loop control method until a constant speed state is reached; estimating an angle difference, wherein the angle difference is a difference value between an actual position and an open-loop position of a rotor of the motor; and obtaining the motor load based on the angle difference and a load estimation model, the load estimation model being obtained based on a previous calibration test. According to the configuration, the motor load is reversely deduced through the internal relation between the angle difference and the motor load when the motor moves at a constant speed, on one hand, the advantage that the non-inductive permanent magnet synchronous motor does not need a sensor is reserved, and on the other hand, the problem that a method for obtaining the motor load of the non-inductive permanent magnet synchronous motor is lacked in the prior art is solved; necessary information is provided for subsequent control optimization of the motor, and the beneficial effects of energy conservation and environmental protection are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of inductive permanent magnet synchronous motor control, and in particular to a motor load estimation method and a readable storage medium. Background Art

[0002] In some devices, sensorless permanent magnet synchronous motors are used as drive motors. For example, some models of washing machines are driven by sensorless permanent magnet synchronous motors. Sensorless permanent magnet synchronous motors refer to permanent magnet synchronous motors without position sensors. For this type of motor, on the one hand, the reduction of sensors increases the application range of the motor, but on the other hand, it also puts higher requirements on the control algorithm.

[0003] During the operation of the equipment, it is sometimes necessary to know the size of the motor load in order to optimize the control effect. For example, during the complete washing process of a washing machine, the weight of the clothes remains unchanged, but the motor needs to be started frequently. If the weight of the clothes in the washing machine is unknown, the washing machine must use the full-load start mode each time it is started. If there is a method to know the weight of the clothes in the washing machine at the first start, the subsequent repeated start process can estimate the total load of the motor based on the weight of the clothes and the mass of the various components of the washing machine itself, and better plan the current at startup based on the total load, avoid the full-load start mode, reduce the starting torque, and achieve the beneficial effects of energy saving and environmental protection. However, due to the lack of sensors, other methods are needed to obtain the motor load.

[0004] In summary, in the prior art, there is a lack of an effective method for obtaining the motor load of an inductive permanent magnet synchronous motor. Summary of the invention

[0005] The object of the present invention is to provide a motor load estimation method and a readable storage medium to make up for the lack of a method for obtaining the motor load of an inductive permanent magnet synchronous motor in the prior art.

[0006] In order to solve the above technical problems, the present invention provides a motor load estimation method, which is applied to a motor, wherein the motor is an inductive permanent magnet synchronous motor, and the motor load estimation method comprises: controlling the start of the motor based on a preset open-loop control method until a uniform speed state is reached; estimating an angle difference, wherein the angle difference is the difference between the actual position of the rotor of the motor and the open-loop position; and obtaining the motor load based on the angle difference and a load estimation model, wherein the load estimation model is obtained based on a prior calibration test.

[0007] Optionally, the calibration test steps include: setting a determined given current; setting different motor loads; for each motor load, controlling the motor start-up with the given current based on the preset open-loop control method until a uniform speed state is reached; estimating the angle difference in the same manner as estimating the motor load to obtain a motor load-angle difference data pair; and obtaining the load estimation model based on the motor load-angle difference data pair.

[0008] Meanwhile, the step of controlling the motor startup based on the preset open-loop control method in the motor load estimation method uses the given current to control the motor startup.

[0009] Optionally, the calibration test steps include: setting different given currents and motor loads; for each combination of given currents and motor loads, controlling the start of the motor based on the preset open-loop control method until a uniform speed state is reached; estimating the angle difference in the same manner as estimating the motor load to obtain a given current-motor load-angle difference data pair; and obtaining the load estimation model based on the given current-motor load-angle difference data pair.

[0010] Optionally, the step of estimating the angle difference includes: recording θ when the motor reaches the uniform speed state L as the angle difference.

[0011] Among them, according to the motor balance formula:

[0012]

[0013] Among them, T L is the motor load torque, T e is the electromagnetic torque, n p is the number of pole pairs of the motor, ψ f is the permanent magnet flux of the motor, i q* is the given current of the q axis, θ L is the angle difference, wherein the motor meets the motor balance formula T when the motor reaches the uniform speed state L =T e .

[0014] Optionally, the load estimation model is a model combining a lookup table with linear interpolation, or a linear model.

[0015] Optionally, the step of estimating the angle difference comprises: estimating the actual position of the rotor based on a sliding mode observer algorithm, or estimating the actual position of the rotor based on a sensorless algorithm. Estimating an open-loop angular velocity based on a position generator. Obtaining an open-loop position of the rotor based on an integral of the open-loop angular velocity, and obtaining the angle difference based on a difference between the open-loop position and the actual position.

[0016] Optionally, the motor is a driving motor of a washing machine, and the variable item of the motor load is the mass of the clothes placed in the washing machine.

[0017] In order to solve the above technical problem, the present invention further provides a readable storage medium, on which a program is stored. When the program is run, the above motor load estimation method is executed.

[0018] Compared with the prior art, the present invention provides a motor load estimation method and a readable storage medium, wherein the motor load estimation method includes: controlling the motor to start based on a preset open-loop control method until a uniform speed state is reached; estimating an angle difference, wherein the angle difference is the difference between the actual position of the rotor of the motor and the open-loop position; and obtaining the motor load based on the angle difference and a load estimation model, wherein the load estimation model is obtained based on a prior calibration test. With such a configuration, the motor load is inferred through the intrinsic connection between the angle difference and the motor load when the motor is moving at a uniform speed. On the one hand, the advantage of the inductive permanent magnet synchronous motor that does not require a sensor is retained, and on the other hand, the problem of the lack of a method for obtaining the motor load of the inductive permanent magnet synchronous motor in the prior art is solved, and necessary information is provided for subsequent control optimization of the motor, achieving the beneficial effects of energy saving and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0020] Figure 1 4 is a flow chart of a method for estimating motor load according to an embodiment of the present invention.

[0021] Figure 2 4 is a control block diagram of a preset open-loop control method according to an embodiment of the present invention.

[0022] Figure 3a It is a schematic diagram of various parameters in the initial state of an embodiment of the present invention.

[0023] Figure 3b It is a schematic diagram of various parameters and a schematic diagram of angle difference during forward rotation operation according to an embodiment of the present invention.

[0024] In the attached figure: U2-Park inverse transformation module; U3-space vector PWM module. DETAILED DESCRIPTION

[0025] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.

[0026] As used in the present invention, the singular forms "one", "an" and "the" include plural objects, the term "or" is generally used to include the meaning of "and / or", the term "several" is generally used to include the meaning of "at least one", and the term "at least two" is generally used to include the meaning of "two or more". In addition, the terms "first", "second" and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" and "third" may explicitly or implicitly include one or at least two of the features, "one end" and "the other end" and "the proximal end" and "the distal end" generally refer to two corresponding parts, which include not only the endpoints, and the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. In addition, as used in the present invention, an element disposed on another element generally only indicates that there is a connection, coupling, cooperation or transmission relationship between the two elements, and the connection, coupling, cooperation or transmission between the two elements may be direct or indirect through an intermediate element, and cannot be understood as indicating or implying the spatial position relationship between the two elements, that is, one element may be in any orientation such as inside, outside, above, below or on one side of another element, unless otherwise clearly indicated in the content. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] The core idea of ​​the present invention is to provide a motor load estimation method and a readable storage medium to make up for the lack of a method for obtaining the motor load of an inductive permanent magnet synchronous motor in the prior art.

[0028] The following description is given with reference to the accompanying drawings.

[0029] Please refer to Figure 1 This embodiment provides a motor load estimation method, which is applied to a motor, wherein the motor is an inductive permanent magnet synchronous motor, and the motor load estimation method includes:

[0030] S10, controlling the motor to start based on a preset open-loop control method until a uniform speed state is reached.

[0031] S20, estimating an angle difference, where the angle difference is a difference between an actual position of the rotor of the motor and an open-loop position.

[0032] And, S30, obtaining the motor load based on the angle difference and a load estimation model, wherein the load estimation model is obtained based on a previous calibration test.

[0033] In step S10, the open-loop control method is preset as Figure 2 As shown. The open-loop control curve outputs a given current iq*, which can be used as the current for starting the permanent magnet synchronous motor in an open-loop manner. The reference current id* delivered to the d-axis can be given as 0. The current iq* and the current id* are respectively differentially calculated with the feedback currents iq and id, and then proportional integral (PI) calculations are performed to generate the voltage u q and u d , used to represent the q-axis and d-axis voltages in the (d,q) coordinate system. Voltage u q 、u d Can be used in the Park inverse transformation module U2 to generate a voltage u according to the Park inverse transformation α 、u β , used to represent the voltages on the α and β axes in the (α, β) coordinate system; the voltage u α 、u β The Clarke inverse transformation and space vector PWM (SVPWM) module U3 can be used to generate three pulse width modulation signal (PWM) waveforms according to the Clarke inverse transformation, and then the three-phase terminal voltage u is generated after the driving capability is increased by the inverter bridge module (not shown). a 、u b 、u c , as the driving power input to the permanent magnet synchronous motor (PMSM). On the other hand, the open loop control curve outputs the angular velocity ω* and integrates it to obtain the angle θ* as the input parameter of the Park inverse transformation module U2.

[0034] The specific scheme of the open-loop control can be selected according to actual needs, for example, IF start, VF start, etc. The preset open-loop control method in step S10 is the same as the start method when calibrating the load estimation model. IF start is taken as an example below to introduce the scheme of the present invention. It can be understood that replacing IF start with VF start, or other open-loop control methods, does not affect the beneficial effects of the present invention, and there is no replacement cost. The scheme of the present invention can be applied to various open-loop control start-up inductive permanent magnet synchronous motors.

[0035] The theoretical basis of this embodiment is analyzed as follows:

[0036] Taking the surface-mount motor as an example, IF start is a more suitable start control method for permanent magnet synchronous motors. It performs closed-loop control on the current and open-loop control on the speed. The angular velocity ω* is integrated to obtain the angle θ*, but this angle is not the actual position of the rotor, but an open-loop position. The specific control block diagram of IF start can be found according to Figure 2 to understand the content.

[0037] The given current of the d-axis is set to 0, that is, i d* =0, the given current of the q axis is set to a constant value i q* , this value should overcome the load T L , to ensure that the motor can start normally.

[0038] After the rotor is pre-positioned, the rotor is at the zero initial position, the angular velocity ω* is provided by the position generator, the open-loop angle is defined as θ*, and the relationship between position and angle is:

[0039]

[0040] Among them, ω * =∫adt.

[0041] Where a is the angular acceleration of the q* axis of the coordinate system. a can be started with linear or nonlinear acceleration according to the motor characteristics. Figure 3a As shown, the q axis is the real coordinate axis of the rotor, and q* is the given coordinate axis. The q* axis is lagged behind the q axis by 90°. The i generated at the initial moment is q is zero, and the electromagnetic torque is zero, which is beneficial to reduce speed fluctuation and start smoothly. L is the angle between the q axis and q*, the power angle δ is the angle between the d axis and the q* axis, θ L The relationship with δ is δ=π / 2-θ L Because the motor has an initial load, including the resistance caused by friction, the motor is initially stationary. As the q* axis rotates, the power angle δ gradually increases, the angle with the real axis becomes smaller, and the electromagnetic torque increases. When the electromagnetic torque is greater than T L When the load torque is less than the maximum electromagnetic torque that the motor can generate, there must be a certain δ that makes the system balanced, thus achieving Figure 3b The status shown. Figure 3b In, θ L That is, the angle differences, α and β represent the directions of the coordinate axes.

[0042] The electromagnetic torque T of the motor e Calculate according to the following formula:

[0043]

[0044] n pis the number of pole pairs of the motor, ψ f is the permanent magnet flux of the motor, is the given current of the q axis. When the motor moves at a constant speed, the motor balance formula is satisfied, that is, the motor load torque T L =Electromagnetic torque T in the above formula e That is, when the motor passes through, for example Figure 2 When the open-loop control method starts and reaches uniform rotation, estimate the angle difference θ of the motor at this time L , the angle difference θ at this time L It directly reflects the motor load. There are two ways to interpret this formula. (1) If i is fixed q* , due to n p and ψ f are all constants, then T L Only and θ L About, that is, T L =f(θ L ). (2) If i is not fixed q* , then T L =f(i q* ,θ L ).

[0045] Based on the above understanding, the load estimation model can be obtained in two different ways.

[0046] The first solution is that the calibration test step includes: setting a certain given current (such as the given current of the q axis mentioned above) ); set different motor loads; for each motor load, control the motor to start with the given current based on the IF control method until a uniform speed state is reached; estimate the angle difference in the same way as when estimating the motor load, and obtain a motor load-angle difference data pair; and obtain the load estimation model based on the motor load-angle difference data pair. It is worth noting here that in order to calibrate the load estimation model, the motor load set here is a given motor load. Taking the driving motor of a washing machine as an example, it can be a given load clothing weight, not the motor load torque T in the aforementioned motor balance formula. L The present invention estimates the aforementioned angle difference θ when the motor load (such as the weight of the clothes) is given and the motor is started in an open loop to reach a load balance state (i.e., a uniform speed state). L , a motor load estimation model can be established.

[0047] Meanwhile, the step of controlling the motor start-up based on the IF control method in the motor load estimation method uses the given current to control the motor start-up.

[0048] The second solution is that the calibration test step includes: setting different given currents (such as the given current of the q axis mentioned above) ) and motor load; for each set of given current and motor load combinations, control the motor to start based on the IF control method until a uniform speed state is reached; estimate the angle difference in the same manner as when estimating the motor load, and obtain a given current-motor load-angle difference data pair; and obtain the load estimation model based on the given current-motor load-angle difference data pair. The motor load set here is a given motor load, which can be a given load clothing weight, taking the driving motor of a washing machine as an example.

[0049] The two solutions have their own advantages. The first solution can simplify the calibration test process and the motor load estimation process. The second solution is more applicable and can be applied to scenarios with large motor load spans and / or where the given current is not fixed (for example, the given current may need to be combined with other algorithms).

[0050] Since the motor moves at a constant speed, T L =T e , the above process can be understood as: According to the motor balance formula:

[0051]

[0052] Among them, T L is the motor load torque, T e is the electromagnetic torque, n p is the number of pole pairs of the motor, ψ f is the permanent magnet flux of the motor, i q* is the given current of the q axis, θ L is the angle difference, wherein when the motor reaches the uniform speed state, T L =T e .

[0053] It is worth noting that in order to calibrate the load estimation model, the motor load set here is a given motor load. Taking the driving motor of a washing machine as an example, it can be a given load clothing weight, not the motor load torque T in the above motor balance formula. L The present invention estimates the aforementioned angle difference θ when the motor load (such as the weight of the clothes) is given and the motor is started in an open loop to reach a load balance state (i.e., a uniform speed state). L , then a motor load estimation model can be established, such as (load weight, θ L The load estimation model is a model that combines a query table with linear interpolation, or a simple linear model is used directly. The motor load weight (such as the weight of clothes) when the motor is actually running can be used to estimate the angle difference θ when the motor actually runs at a uniform speed. LBy entering the motor load estimation model into the table or linear interpolation fitting, the motor load weight during actual operation can be obtained.

[0054] In order to speed up the operation, the inventor believes that the error caused by using a linear model does not affect the actual use effect, so the better solution is that the load estimation model is a linear model. In this way, the module for executing the motor load estimation method can be implemented by a simple logic circuit or even an analog circuit.

[0055] The actual position of the rotor can be realized by a related estimation method. For example, the actual position of the rotor is estimated based on a sliding mode observer algorithm, or the actual position of the rotor is estimated based on a sensorless algorithm such as a Lomborg algorithm. The specific implementation of the above algorithm can be understood according to common knowledge in the art.

[0056] On the other hand, the step of estimating the angle difference further includes: acquiring an open-loop angular velocity based on a position generator; and acquiring an open-loop position of the rotor based on an integral of the open-loop angular velocity.

[0057] In a specific embodiment, the motor is a driving motor of a washing machine, and the variable term of the motor load is the mass of the clothes placed in the washing machine. After the motor load is calculated, the motor load when the washing machine is unloaded (which can be calibrated at the factory) can be subtracted to calculate the mass or weight of the clothes.

[0058] This embodiment further provides a readable storage medium, on which a program is stored. When the program is run, the above-mentioned motor load estimation method is executed.

[0059] In summary, the present embodiment provides a motor load estimation method and a readable storage medium. Among them, the motor load estimation method includes: controlling the motor start-up based on the IF control method until a uniform speed state is reached; estimating the angle difference, the angle difference being the difference between the actual position of the rotor of the motor and the open-loop position; and obtaining the motor load based on the angle difference and the load estimation model, wherein the load estimation model is obtained based on a prior calibration test. With such a configuration, the motor load is inferred through the intrinsic connection between the angle difference and the motor load when the motor is moving at a uniform speed. On the one hand, the advantage of the inductive permanent magnet synchronous motor that does not require a sensor is retained, and on the other hand, the problem of the lack of a method for obtaining the motor load of the inductive permanent magnet synchronous motor in the prior art is solved, which provides necessary information for the subsequent control optimization of the motor and achieves the beneficial effects of energy saving and environmental protection.

[0060] The above description is only a description of the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for estimating motor load, characterized in that: Applied to a motor, the motor is an inductive permanent magnet synchronous motor, and the motor load estimation method includes: Controlling the motor to start based on a preset open-loop control method until a uniform speed state is reached; estimating an angle difference, the angle difference being the difference between an actual position and an open-loop position of a rotor of the motor; and, The motor load is obtained based on the angle difference and a load estimation model, wherein the load estimation model is obtained based on a previous calibration test.

2. The motor load estimation method according to claim 1, characterized in that: The steps of the calibration test include: Set a certain given current; Set different motor loads; For each motor load, controlling the motor to start with the given current based on the preset open-loop control method until a uniform speed state is reached; estimating the angle difference in the same manner as estimating the motor load to obtain a motor load-angle difference data pair; and, Obtaining the load estimation model based on the motor load-angle difference data pair; Meanwhile, the step of controlling the motor startup based on the preset open-loop control method in the motor load estimation method uses the given current to control the motor startup.

3. The motor load estimation method according to claim 1, characterized in that: The steps of the calibration test include: Set different given current and motor load; For each combination of a given current and a motor load, controlling the motor to start based on the preset open-loop control method until a uniform speed state is reached; The angle difference is estimated in the same manner as when estimating the motor load, to obtain a given current-motor load-angle difference data pair; and, The load estimation model is obtained based on the given current-motor load-angle difference data pairs.

4. The motor load estimation method according to claim 2 or 3, characterized in that: The step of estimating the angle difference includes recording the angle when the motor reaches the uniform speed state. L As the angle difference, Among them, according to the motor balance formula: Among them, T L is the motor load torque, T e is the electromagnetic torque, n p is the number of pole pairs of the motor, ψ f is the permanent magnet flux of the motor, i q* is the given current of the q axis, θ L is the angle difference, wherein when the motor reaches the uniform speed state, the balance formula T of the motor is satisfied. L =T e .

5. The motor load estimation method according to claim 4, characterized in that: The load estimation model is a model combining a lookup table with linear interpolation, or a linear model.

6. The motor load estimation method according to claim 1, characterized in that: The step of estimating the angle difference comprises: estimating the actual position of the rotor based on a sliding mode observer algorithm, or estimating the actual position of the rotor based on a sensorless algorithm; Get open-loop angular velocity based on the position generator; Obtaining an open-loop position of the rotor based on an integral of the open-loop angular velocity; and The angle difference is obtained based on a difference between the open-loop position and the actual position.

7. The motor load estimation method according to claim 1, characterized in that: The motor is a driving motor of a washing machine, and the variable item of the motor load is the mass of the clothes placed in the washing machine.

8. A readable storage medium, characterized in that: The readable storage medium stores a program, and when the program is executed, the motor load estimation method according to any one of claims 1 to 7 is executed.

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